U.S. Pat. No. 4,371,857 describes a ram actuator having a movable ram member which includes a series of spaced apart magnetizable sections or inserts. The ram member is movably supported within a yoke structure that provides a series of gaps between opposed magnetic poles for cooperating with the magnetizable inserts of the ram member. An electrical coil arrangement on the yoke is activatable to generate magnetic flux through the yoke and its pole pieces to interact with the magnetizable sections of the ram member to produce a rapid acceleration of the ram member as an output stroke. The underlying principles of operations of such an actuator are described in connection with FIG. 6 of that patent.
U.S. Pat. No. 4,412,197 describes a ram actuator similar to that of U.S. Pat. No. 4,371,857, but wherein the electromagnetic yoke structure comprises a pair of yoke halves of the E shaped cross section, wherein the three legs of the E provide the gap-forming poles. The activating coil is supplied as a prewound toroidal body that is shaped to fit over the center leg of the E and be confined within the space between the center leg and the two outer legs. This arrangement contributes to the compactness and ease of assembly of the ram actuator.
It is an object of the present invention to provide a ram actuator having a compact geometry suitable for assembly into a multi-actuator bank and having easy to install toroid-like coils similar to those described in U.S. Pat. No. 4,412,197, but having enhanced electromagnetic efficiency.
Another object of this invention to provide a ram actuator that can achieve an electromagnetic actuating force equal to that produced by the arrangement of U.S. Pat. No. 4,371,857 with a smaller more compact structure.